n = int(input())
c = list(input())

x = c.count("R")

ans = 0
for i in range(x):
    if c[i] == "W":
        ans += 1

print(ans) n = int(input()) n int(input()) int input() input c = list(input()) c list(input()) list input() input x = c.count("R") x c.count("R") c.count c count "R" ans = 0 ans 0 for i in range(x):
    if c[i] == "W":
        ans += 1 i range(x) range x if c[i] == "W":
        ans += 1 c[i] == "W" c[i] c i "W" ans += 1 ans 1 print(ans) print ans ans = 0 0 ans n = int(input()) int(input()) n c = list(input()) list(input()) c ans += 1 1 ans x = c.count("R") c.count("R") x
n = int(input())
c = list(input())

x = c.count("R")

ans = 0
for i in range(x):
    if c[i] == "W":
        ans += 1

print(ans)